Polymorphism in Java

📍 Polymorphism allows a single interface to be used for different types of actions.

📍 It is of two types:

Method Overloading (Compile-time Polymorphism)

Method Overriding (Runtime Polymorphism)


*Method Overloading* (Same method name, different parameters)

class MathOperations {
int add(int a, int b) {
return a + b;
}

double add(double a, double b) {
return a + b;
}
}

*Method Overriding* (Same method in parent and child class)

class Animal {
void makeSound() {
System.out.println("Animal makes a sound");
}
}

class Dog extends Animal {
void makeSound() {
System.out.println("Dog barks");
}
}

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🚀 Roadmap to Become a Java Developer 🔰

📂 Programming Basics
 ∟📂 Master Java Syntax, Variables & Data Types
  ∟📂 Learn Control Flow, Loops & Exception Handling
   ∟📂 Practice with Basic Programs

📂 Object-Oriented Programming (OOP)
 ∟📂 Understand Classes, Objects & Inheritance
  ∟📂 Dive into Encapsulation, Polymorphism & Abstraction
   ∟📂 Explore Design Patterns in Java

📂 Tools & Build Systems
 ∟📂 Get Comfortable with IDEs (e.g., IntelliJ, Eclipse)
  ∟📂 Master Maven & Gradle for Dependency Management
   ∟📂 Learn Git & Version Control Systems

📂 Data Structures & Algorithms
 ∟📂 Learn Java Collections (Lists, Sets, Maps, etc.)
  ∟📂 Understand Algorithms & Problem Solving
   ∟📂 Tackle Coding Challenges

📂 Web Development & APIs
 ∟📂 Learn Servlets & JSP Basics
  ∟📂 Dive into Spring Boot & RESTful Services
   ∟📂 Understand Microservices Architecture

📂 Database & Persistence
 ∟📂 Master JDBC & SQL Fundamentals
  ∟📂 Explore ORM Tools like Hibernate & JPA
   ∟📂 Practice with Real-World Data

📂 Testing & Debugging
 ∟📂 Get Started with JUnit & Test-Driven Development
  ∟📂 Learn Debugging Techniques & Best Practices
   ∟📂 Automate Testing with Tools

📂 Advanced Topics
 ∟📂 Learn Multithreading & Concurrency
  ∟📂 Understand JVM Internals & Garbage Collection
   ∟📂 Explore Performance Optimization

📂 Projects & Real-World Applications
 ∟📂 Build End-to-End Java Applications
  ∟📂 Contribute to Open-Source Projects
   ∟📂 Showcase on GitHub & Portfolio

📂 Interview Preparation & Job Hunting
 ∟📂 Solve Java Coding Challenges
  ∟📂 Master System Design & Architecture Concepts
   ∟📂 Network & Apply for Java Roles

✅️ Get Hired

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Java project ideas to help you practice your skills

1. ToDo List Application: Create a command-line or GUI-based application that allows users to create, manage, and organize their tasks.

2. Calculator: Build a simple calculator application that can perform basic arithmetic operations like addition, subtraction, multiplication, and division.

3. Library Management System: Design a system for managing library resources, including books, patrons, and borrowing records.

4. Chat Application: Develop a chat application that enables users to communicate in real-time, either as a desktop app or through a web interface.

5. Weather App: Create an app that fetches weather data from an API and displays current weather conditions for a given location.

6. Student Gradebook: Build a program to store and calculate student grades. You can add features like grade averages and report generation.

7. Expense Tracker: Create an application for tracking expenses and generating reports, helping users manage their finances.

8. Simple Game (e.g., Tic-Tac-Toe): Implement a classic game like Tic-Tac-Toe to learn about game logic and user interaction.

9. Blog or Content Management System (CMS): Build a simple blog or CMS where users can create, edit, and publish articles.

10. E-commerce Shopping Cart: Create a basic online shopping cart system with product listings, a shopping cart, and checkout functionality.

11. File Manager: Develop a file manager application that allows users to organize and manage files and directories on their computer.

12. Inventory System: Design an inventory management system for tracking products, quantities, and orders for a small business.

13. Music Player: Create a basic music player with features like play, pause, skip, and a library of songs.

14. Password Manager: Build a secure application for storing and managing passwords and other sensitive information.

15. Chess or Sudoku Solver: Implement a chess game or a Sudoku puzzle solver to delve into complex algorithms and logic.

16. Note-taking App: Develop a note-taking application with features like creating, editing, and organizing notes.

17. Expense Sharing App: Build an app for groups to track shared expenses and split bills among friends or roommates.

18. Task Scheduler: Create a program that allows users to schedule and manage tasks, reminders, and appointments.

19. Mini Social Media Platform: Create a simplified social media platform with features like user profiles, posting, and commenting.

20. Quiz or Flashcard Application: Design an app for creating and taking quizzes or using flashcards to study various topics.

Choose a project that aligns with your interests and skill level. As you work on these projects, you'll gain valuable experience and improve your Java programming skills.

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Topics Covered in this E-Book

Chapter - 1 : Introduction to Java
Chapter - 2 : Getting Started with Java
Chapter - 3 : Control Structures
Chapter - 4 : Functions and Methods
Chapter - 5 : Object-Oriented in Java
Chapter - 6 : Collections and Generics
Chapter - 7 : Multithreading and Concurrency
Chapter - 8 : File I/O and Data Persistence
Chapter - 9 : User Interfaces with JavaFX
Chapter - 10 : Advanced Topics

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List of Java Project Ideas 💡👨🏻‍💻☕

Beginner Projects

🔹 Calculator
🔹 To-Do List App
🔹 Number Guessing Game
🔹 Password Generator
🔹 Flashcard Quizzer
🔹 Simple Chatbot
🔹 Weather App
🔹 Unit Converter
🔹 Rock-Paper-Scissors Game

Intermediate Projects

🔸 Personal Diary
🔸 Web Scraping Tool
🔸 Expense Tracker
🔸 Spring Boot Blog
🔸 Image Gallery
🔸 Chat Application
🔸 Pomodoro Timer
🔸 Basic Game with JavaFX

Advanced Projects

🔺 Social Media Dashboard
🔺 Machine Learning Model
🔺 Data Visualization Tool
🔺 Blockchain Simulation
🔺 Chatbot with NLP
🔺 File Organizer

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✅ List and Set in Java Collections Framework :

🔅 LIST :

🔸 List in Java provides the facility to maintain the ordered collection.

🔹 It contains the index-based methods to insert, update, delete and search the elements.

🔸 It can have the duplicate elements also.

🔹 We can also store the null elements in the list.

🔅 SET :

🔸 Set interface in Java is present in jave.util package.

🔹It extends the Collection interface.

🔸 It represents the unordered set of elements which doesn't allow us to store the duplicate items.

🔹 We can store at most one null value in Set.

🔸 Set is implemented by HashSet, LinkedHashSet and TreeSet.

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🚀 PERFORMANCE TUNING: Boost Your System Like a Pro! ⚡️

Is your application slow? Facing database bottlenecks? Or maybe network issues? Performance tuning is the key! Here’s a breakdown of essential optimization areas to supercharge your system:

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Optimize your code by managing CPU, memory, and other resources efficiently. A few tweaks can make a BIG difference!

🔹 Infrastructure Tuning 🏗
Benchmark, scale, and optimize storage to ensure your hardware and cloud infrastructure are performing at their best.

🔹 Architecture Tuning ☁️
Implement caching, loose coupling, and asynchronous processing for a seamless and scalable system.

🔹 Configuration Tuning ⚙️
Fine-tune your app's settings for maximum efficiency—master configuration tuning is crucial!

🔹 Network Tuning 🌐
Reduce latency, optimize traffic flow, and secure your network with firewall & DNS adjustments.

🔹 Database Tuning 🗄
Optimize queries, indexes, and partitions to speed up data retrieval and improve overall DB performance.

2 Month Roadmap to learn Java and Spring from basics to advanced

Week 1-2: Core Java

- Basic Syntax: Data types, operators, loops (for, while, do-while)
- OOP Concepts: Classes, objects, inheritance, polymorphism, encapsulation, abstraction
- Collections Framework: List, Set, Map, Queue, Iterator, etc.
- Exception Handling: Try-catch, custom exceptions, multi-catch
- File I/O: Reading/writing files using java.io and java.nio
- Java 8+ Features: Lambdas, Streams, Optional, Functional Interfaces
- Multithreading: Threads, Runnable, ExecutorService, Future, and basic synchronization

Week 3-4: Advanced Java & JDBC

- JVM Internals: ClassLoader, JIT, memory management, garbage collection
- Generics: Usage and wildcards
- Design Patterns: Singleton, Factory, Strategy, Observer, Dependency Injection (Intro)
- JDBC: Connecting with databases (CRUD operations), PreparedStatement, Connection pooling

Week 5-6: Spring Framework (Basics)

- Spring Core
- Dependency Injection (DI) and Inversion of Control (IoC)
- Beans, Scopes, and Bean Life Cycle
- Autowiring and Spring Annotations
- Spring AOP: Aspect-Oriented Programming fundamentals
- Spring Data JPA: Basic CRUD operations with JPA
- Entities, Repositories, and Custom Queries

Week 7: Spring Boot (Basics)

- Spring Boot Fundamentals: Understanding the Spring Boot architecture
- REST API creation
- Spring Boot Annotations (@RestController, @RequestMapping, etc.)
- Running a Spring Boot application
- Spring Boot Auto Configuration: Application properties and profiles
- Spring Boot with Database: Integrate Spring Boot with MySQL using Spring Data JPA

Week 8: Spring Boot (Advanced)

- Security: Introduction to Spring Security (Basic Authentication)
- Advanced Spring Boot Features: Exception handling (@ControllerAdvice)
- Logging with Spring Boot
- Pagination and Sorting
- Testing: Write unit tests using JUnit and Mockito in Spring Boot

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Java Basics every beginner should learn to build a strong foundation:

1. Hello World & Setup

Install JDK and an IDE (like IntelliJ or Eclipse)

Write your first program: public class HelloWorld

2. Data Types & Variables

Primitive types: int, double, char, boolean

Non-primitive types: String, Arrays, Objects

Type casting (implicit & explicit)

3. Operators

Arithmetic: + - * / %

Comparison: == != > < >= <=

Logical: && || !

4. Control Flow

If, else if, else

Switch-case

Loops: for, while, do-while

break and continue

5. Functions (Methods)

Syntax: public static returnType methodName(params)

Method overloading

Return types & parameter passing

6. Object-Oriented Programming (OOP)

Classes & Objects

this keyword

Constructors (default & parameterized)

7. OOP Concepts

Encapsulation (private variables + getters/setters)

Inheritance (extends keyword)

Polymorphism (method overriding)

Abstraction (abstract classes & interfaces)

8. Arrays & ArrayList

Declaring and iterating arrays

ArrayList methods: add, remove, get, size

Multidimensional arrays

9. Exception Handling

Try-catch-finally blocks

throw and throws

Custom exceptions

10. Basic Input/Output

Scanner class for user input

System.out.println() for output

Free Java Resources: https://whatsapp.com/channel/0029VamdH5mHAdNMHMSBwg1s

ENJOY LEARNING 👍👍

Typical java interview questions sorted by experience


Junior
* Name some of the characteristics of OO programming languages
* What are the access modifiers you know? What does each one do?
* What is the difference between overriding and overloading a method in Java?
* What’s the difference between an Interface and an abstract class?
* Can an Interface extend another Interface?
* What does the static word mean in Java?
* Can a static method be overridden in Java?
* What is Polymorphism? What about Inheritance?
* Can a constructor be inherited?
* Do objects get passed by reference or value in Java? Elaborate on that.
* What’s the difference between using == and .equals on a string?
* What is the hashCode() and equals() used for?
* What does the interface Serializable do? What about Parcelable in Android?
* Why are Array and ArrayList different? When would you use each?
* What’s the difference between an Integer and int?
* What is a ThreadPool? Is it better than using several “simple” threads?
* What the difference between local, instance and class variables?

Mid
* What is reflection?
* What is dependency injection? Can you name a few libraries? (Have you used any?)
* What are strong, soft and weak references in Java?
* What does the keyword synchronized mean?
* Can you have “memory leaks” on Java?
* Do you need to set references to null on Java/Android?
* What does it means to say that a String is immutable?
* What are transient and volatile modifiers?
* What is the finalize() method?
* How does the try{} finally{} works?
* What is the difference between instantiation and initialisation of an object?
* When is a static block run?
* Why are Generics are used in Java?
* Can you mention the design patterns you know? Which of those do you normally use?
* Can you mention some types of testing you know?

Senior
* How does Integer.parseInt() works?
* Do you know what is the “double check locking” problem?
* Do you know the difference between StringBuffer and StringBuilder?
* How is a StringBuilder implemented to avoid the immutable string allocation problem?
* What does Class.forName method do?
* What is Autoboxing and Unboxing?
* What’s the difference between an Enumeration and an Iterator?
* What is the difference between fail-fast and fail safe in Java?
* What is PermGen in Java?
* What is a Java priority queue?
* *s performance influenced by using the same number in different types: Int, Double and Float?
* What is the Java Heap?
* What is daemon thread?
* Can a dead thread be restarted?

Source: medium.